const fs = require('fs');
const path = require('path');

const IMAGE_EXTENSIONS = new Set(['.jpg', '.jpeg', '.png', '.gif', '.bmp', '.tiff', '.tif', '.webp', '.heic', '.heif']);

function listImages(folderPath) {
  return fs.readdirSync(folderPath)
    .filter(fileName => IMAGE_EXTENSIONS.has(path.extname(fileName).toLowerCase()))
    .map(fileName => {
      const fullPath = path.join(folderPath, fileName);
      const stat = fs.statSync(fullPath);
      return { name: fileName, path: fullPath, mtime: stat.mtimeMs };
    })
    .sort((a, b) => a.name.localeCompare(b.name, 'ko'));
}

function readImageAsDataUrl(filePath) {
  const data = fs.readFileSync(filePath);
  const mime = getImageMime(path.extname(filePath));
  return `data:image/${mime};base64,${data.toString('base64')}`;
}

function getImageMime(extName) {
  const ext = extName.toLowerCase().replace('.', '');
  if (ext === 'jpg' || ext === 'jpeg') return 'jpeg';
  if (ext === 'png') return 'png';
  if (ext === 'gif') return 'gif';
  if (ext === 'webp') return 'webp';
  if (ext === 'tiff' || ext === 'tif') return 'tiff';
  if (ext === 'bmp') return 'bmp';
  if (ext === 'heic' || ext === 'heif') return 'heic';
  return 'jpeg';
}

function fileExists(filePath) {
  try {
    fs.accessSync(filePath);
    return true;
  } catch {
    return false;
  }
}

function moveFileWithCopyFallback(src, dest) {
  try {
    fs.renameSync(src, dest);
  } catch (e) {
    if (e.code !== 'EXDEV') throw e;
    fs.copyFileSync(src, dest);
    fs.unlinkSync(src);
  }
}

module.exports = {
  fileExists,
  listImages,
  moveFileWithCopyFallback,
  readImageAsDataUrl,
};